cat limping from injury?

my 7 year old cat Whitey was injured about 2-3 weeks ago when a 70+lb dog we are dog sitting accidentally landed on his shoulder area. he strongly favors his front left paw and limps whenever he walks. he is eating and drinking fine and going to the bathroom fine, he CAN physically move that leg, doesnt seem to have any problems grooming himself and even lays on his left side from time to time when sleeping. it does not appear to be dislocated because when looking at him, his leg looks fine, doesnt look "out of place", isnt dangling or anything. the only time you can tell he got hurt is when he walks (limping, with his front left paw help up). from what i have been reading online, limps tend to only last a few days, but its been some 2-3 weeks. due to recent financial issues we have not been able to afford to see the vet as of yet and i havent found a vet so far that accepts payment plans. i was just curious if anyone has any idea if this might be a sprain, strain, etc? obviously it hurts because he is limping and i know cats dont show pain as easily as humans and other species...but if it were more serious than a sprain/strain then i dont think he would be able to lay on his left side. he is an indoor/outdoor cat and ever since the injury we strictly prohibited him from going outside. is there anything we can do at home to help it heal, whatever it may be?

OUCH. Poor guy. Other than what you're already doing at home, I don't know of any other advice to give you. He's obviously hurting and something is wrong. Only a vet would be able to tell you exactly what the matter is.