Injured feral cat

Hi, I'm new here and was hoping to get some advice from some of you more experienced with caring for ferals.
About 9 months ago, I discovered a very tiny kitten living under our front porch. We live in a somewhat rural area and I suppose she wondered off from her litter and got lost. Well, I'm a sucker for kitties, so I started leaving food out under the porch. We already have an inside cat and had a dog so what's one more mouth to feed, I figured! Well, between the months of tuna, dry food, regular interaction with our dog (may he RIP), she became a permanent resident.
About 4 months ago, I realized she was in fact female and decided to go ahead and purchase a trap. I trapped her, brought her to the vet and she was spayed and received her vaccinations.
She is probably about a year old now and her and I have bonded well, she comes running for me when she smells me outside smoking or hears my special call for wet food. She lets me pet and scratch her, not pick her up, but will timidly venture into my lap on occasions, and walks in front of my feet when she knows I'm coming to feed her.
Anyway, yesterday I didn't see her at all. I left her wet food and tried to call her, the kids and I looked around but couldn't find her. The day before we had lots of bad weather come through. This morning I called her and she eventually came to me and there is a large gash on the side of her thigh and she has some yuck in one eye. She is walking and putting weight on her leg, but is definitely limping. I assume she and another animal, whether it was a cat, possum, raccoon, I don't know got into a little brawl.

My question is what is the best way to help her heal from the wound? I have yet to ever try to put her in a regular carrier and would like to avoid the vet since it doesn't seem too bad. Since she is outside, I know the wound will get dirty and I'm assuming yesterday she was underneath it shed recouperating, but laying in a lot of dirt and debris. I went and got some tuna and just fed that to her, thinking that the omegas and protein would help, but does anyone have any other suggestions for caring for her injury? It's a large gash, and it's matted from her fur. Nothing seems to be oozing, but has dried up.

Thanks in advance!
Meghan

Hi!! Welcome!! 

First off, thank you so much for caring for this little girl and getting her spayed and vaccinated. You did her a huge favor by doing so!! 

Her interaction with you has helped build trust . That's a very good thing. She really should see a vet. That gash could become infected. She may need to be put on antibiotics. I'd trap her again or if she will let you put her into a carrier to take her in. It's better to be safe than sorry. The vet that spayed and vaccinated her may give you a price break since she's an outdoor cat. The gunk in her eye could be feline herpes. http://pets.webmd.com/cats/feline-herpes-symptoms-treatment

This little girl is not a true feral since she is comfortable being around you and letting you touch her. Is there any chance that you would make her an indoor cat?? Many outdoor cats make the transition very well and many come to prefer being inside where there is guaranteed meals and a safe, warm, dry place to sleep. Outdoor cats have very difficult lives as you've seen by her injury. 

If you care considering bringing her in, we have a very helpful article about introducing cats to each other here 

http://www.thecatsite.com/a/how-to-successfully-introduce-cats-the-ultimate-guide

Again, thank you for everything you have done for her so far (any pictures to share?  ). She is lucky to have you for a friend. 

Please accept my condolences on the loss of your dog. May he RIP 

I am not sure I would take any chances - I would take her to the vet, just to be safe.

But if you absolutely can't, then see if you can wash the wound and apply some antibiotic ointment.  I would also prepare a safer, drier place for her to sleep. A Rubbermaid tote with some clean straw inside is OK for summer.  You might want to make a more involved one, with insulation, for winter.  You can tuck it away near the shed or put it on your porch.  It will definitely offer her a better recuperation spot.

Also, never leave food out overnight.  That's one of the things that may be attracting other critters.

Thank you for taking her to be spayed.  Nothing more important!  Is there any way she can come inside to live now?  She sounds socialized enough to make the adjustment.  You'd have to introduce her slowly to your cat but it can work.

Thank you for your replies! I will see how the day progresses and may have to try to introduce her to the carrier. I really disliked the trap, it was huge and bulky and a pain to lug around! And most of all I felt awful "trapping" her inside of it!