Titan No-Limit Hold'em, $0.10/$0.20 (Titan HH Converter by Kreatief)
BB ($20.10) (Hero)
MP2 ($20.37)
Preflop: Hero is BB with K

, 7
MP2 calls $0.20,
4 folds, Hero checks,
Flop: 6

, 9

, 4

( $0.5 )
Hero bets $0.40, MP2 calls $0.40,
Turn: J

( $1.3 )
Hero bets $0.70,
MP2 raises to 2.2, Hero calls $1.50,
River: 7

( $5.7 )
Hero checks,
MP2 bets $3.20, Hero calls $3.20,
Final Pot: $11.50
MP2 was unknown. He limped from UTG. I checked in the big blind with K7s. Two hearts hit the flop so i chose to bet out with my flush draw, he called. On the turn i hit my flush so a i bet, he reraised me.
I had the 2nd nuts and i had to decide if i want to 4bet. We had about 18 dollars left (more than 4 stack-to-pot ratio) and i was not sure if i can call an allin if i 4bet him. His line indicated that he can have the Ace high flush so i chose not to risk and checked/called it down.
Was it too weak? What do you think?