Get it checked out! If this is forward of the main beam this is a stress area (all the loads of of an unsupported bow, rig compression, every wave plowed through etc.). If you have ever seen where cat hulls fail you will know what I mean. I'm also sure most people remember where team philips failed!
It is quite likely that the the knock to the side has opened this up but you need to be sure that there is no crack down into the main hull seam which will propagate with loading. Very simple repair if caught early but remember gelcoat is just a protective coating and not structural, so shouldn't be used to repair any crack going down into the hull seam, just for refinishing afterwards. If your not sure about tackling this give AW sailboats a call.

Cheshirecatman