I NEED HELPs

So I just recently got two cats. Sebastian and Aurora are their names and these two are very sneaky. Last night, I dont know how it happened but my sister sat on Sebastians leg. I have been freaking out, because I think its been dislocated but it seems to still be in place. He wont step on it and it doesnt seem to be hurting him. He is still as active as ever, he just wont us the leg for some reason and im very very worried. Its just sitting their and he doesnt try to move it.
im not a bad pet owner, im just new to this and my friends say I shouldnt take him to the vet, but im still worried out of my mind. Please help me...

Why would they suggest not taking him to the vet? He absolutely needs to be seen by a vet. Cats are small and humans are pretty big and heavy in comparison - especially if he won't use the leg, it's causing him pain and discomfort that a vet can at least alleviate to some degree. Worst case scenario, it's broken. If he doesn't see a vet, you won't know the extent of the damage and it could heal out of place and cause him long term discomfort.

My friend said not to take him to the vet because he, as well as I, figured it was just dislocated. Thank you for setting this straight, I am taking him today.

Yes, to let a vet examine the leg is the only wise.   With a little luck it may go over by itself, if there was no real damage.  But if there WAS a damage...

True, vet help costs, especielly if he was hurt for real, but such is life. 

Good luck!

ps.   Dislocated sounds as a typical vet errand!  If the vet doenst set it right again, it will grow wrongly, giving him a limp and aches forever.