While learning to wing my son hit the board and left a few cracks. Is this something I can put a coat marine epoxy resin on and its good or do I need to dig into the cracks to stop them.

Do not use just resin, it will crack also.

For a quick-n-dirty repair:

Outside sunlight (behind glass windows is OK, glass stops UVs):
- delimit the crack zone with tape
- sand just the paint away in the zone
- cover with Epoxy Solarez (or other UV-curing resin premixed with glass repair kit)
- stretch some PVC clear tape over it to press it in place

Move the repair in the sun for at least 3 minutes (more is better). Try to have only the repair in the sun to avoid overheating the board. I cover the rest of the boards with towels, for instance.
- remove the tapes. cut the repair to release the underlyng tape.
- clean the tape glue with some alcohol
- smooth the repair edges with a good cutter, or sand.

Or you could use tape with a high quality (3M) glue.

Having built boards or 5 years I never used anything but glass cloth (or carbon) for repairs. Then sander coat and sprayed primer. But admitting using epoxy Solaris on repair on eps core surfboard after busy lineup collision. A fin went through the bamboo skin into eps core when on holiday with no repair supply of necessary items other than epoxy Solaris! Did simple repair (following instructions) after lunch break and ready for afternoon session
10 years later it's still lasted ??

Thanks so much guys.

I don't need to do anything but sand the paint off to stop the cracking? Will the UV curing resin get into the cracks and stop them from expanding? Here is another pic.

No the UV resin (which has small glass fibers in it) will act as an extra glass layer. This is why it is a quick-n-dirty, because it will leave a bump.

The cracks are too thin for normal resins to flow into them. To do a proper repair you will have to sand off the glass layers around the cracks, and re-glass it level with the deck.

I have seen special resins in shipshandlers that are supposed to fill cracks in composite boat hulls by capillarity, but I never tested them.

99% sure form that pic its a paint crack, looks watertight I'd just leave it.
Sometimes a non professional repair devalues the board greatly as people see it and wonder if it was foam depth or not. At least with it left alone like that you can tell its a non issue.

But is it soft...?