Make games for him, in addition to the normal coloring and cutting sorts of things. This can be done very cheap!
I do home daycare and my kids fave fave things to do are my muffin tin games and milk/pop caps games. I went to the dollar store, bought muffin tins...a pack of colored pencil top erasers, a few packs of colored paper clips, some colored pom poms..you get the idea. All a dollar. Also a pack of colored construction paper. Use glue, rubber cement, etc (I use glue dots/zots for longevity in daycare)..and put a color of construction paper in each muffin tin section, to coordinate with the colors of your pom poms, erasers or whatever you got that are small items. You are making a sorting game.
By sorting a pile of 50 or so of these items, they have to use the small pincer grasp to pick them up. This develops the small hand muscles that eventually assist all of us with proper pencil holding and scissor holding.
I also use old formula cans (easily decoupaged with water/glue and ripped up tissue paper or wrapping paper, then sprayed with hairspray for a little seal)....then I cut slits in the top of the can cover. I have saved pop caps, milk caps, juice jug, Gatorade and other jug lids for a long time (I always am saving them!!), and I let them sort or just put them in like large pennies.....and you can work your way to actual coins (I can't really do with my 2/3 year old daycare kids for safety reasons with infants around)...
Kids love to use tweezers too to pick up things like pom poms for games like this! Things with beads are good too (counting them, sorting them, etc)
Good luck and don't fret alot about it. Just being aware of it, you will find tons of things you already do...just do them a little more!