Sun Conure toe bubble?

My poor sun conure has what looks like a bubble on his thumb toe - the farthest toe. It's gotten bigger the last 4 days, I thought maybe it was his nails needing a trim that he was being sensitive of his foot, so I trimmed his nails and his limp went away. But I noticed his thumb toe doesn't really touch anything he perches on and he's not really grabbing onto anything with his foot at all, if he can stand on just one leg, he chooses the other.

Is there anything I can do for him at home before he has to go to the vet? I just got him from a friend 3 weeks ago and am starting to think maybe there was a health reason why he was just given away.