If you receive a wound out of a engine based Player Versus Player fight which has been enacted with Rp involved,
you should roleplay some sort of consequence.
However that does not mean in my opinion that everytime your health drops to low whilst sparring with another player you have to rp looking like pin-cushion.

In that case roleplaying "exhaustion" also works in my eyes. You sparred and exercised, you'll need a break, after which you can continue again.
If however you combat seriously (duell with grave background, battles, wars) and get roughed up / clouded that should show in your roleplay for some days after the battle.
On the other hand I tend to ignore wounds and not roleplay them if I received them from fighting NPCs alone (Did a tree in the woods with noone around realy fall down?) / receive them on a peaceful character due to poor Rp / Newbie rampage.
Acting out wounds received by NPC's whilst fighting them in a group should be at the discreetion of the player(s) involved.
Fighters usualy fight NPC's every other day so Rp-ing injuries after every encounter might become tedious and boring after a while.