First off, you should've raised with this hand preflop. Let's digress.

You have position. So you have a couple of options:

You can 3 bet to define your hand. If he caps (which you will call) and leads the turn you should fold, unless you improve. Or if he smooth calls and check-raises, you should fold.

If this player is known to be loose and aggressive, you should passively call him down by letting him bet a weaker King or a draw.

In heads up situations with position against an opponent who has shown strength, I usually prefer line 2.

The 3 bet lead line, costs 2 big bets, but you might not get to the river if he decides to pop the turn. Calling down from his flop raise costs 2.5 big-bets and you get to showdown. You protect yourself from folding the best hand to a bluff.