Villain is same NL25 grinder as my trips post, 25/19/2. Very hard to fold this, but I think I have to against a solid grinder? I really can't see what else to do after his OOP bet on the flop. I can't fold AK here can I?

Poker Room skin
No Limit Holdem Ring game
Blinds: $0.15/$0.25
4 players
Converter

Stack sizes:
Hero: $39.10
Button: $22.45
SB: $18.45
BB: $25.25

Pre-flop: (4 players) Hero is UTG with
Hero raises to $1, 2 folds, BB raises to $3, Hero calls.

Flop: ($6.15, 2 players)
BB bets $4.8, Hero raises to $20, BB calls all-in $17.2, Hero calls.

Turn: :10c ($50.15, 1 player + 1 all-in - Main pot: $50.15)


River: :10d ($50.15, 1 player + 1 all-in - Main pot: $50.15)


Results:
Final pot: $50.15