Bodog 50$ fullring

hero is UTG with KK, villian is MP.

hero raises 4 blinds, UTG+1 calls, villian calls, everybody else folds.

flop is Q94 rainbow

hero pots it, UTG+1 folds, villian raises the amount hero bet, pot is now the same size as hero's stack, villian has hero covered.

what does hero do?