I’ve had my cory for 6 months now, very healthy and cheerful, no problems getting along with my female betta and 2 otos. However, I just noticed yesterday that one of his whiskers is now missing. I specifically bought rounded, smooth gravel for the tank to avoid this but it looks like it happened anyway. 
He seems to be eating okay still, likes to find bloodworms, brine shrimp and flake food that my betta doesn’t grab and loves munching on algae wafers.
My question is: will the whisker grow back? Is there anything I can do to help it grow?