You did very well, and your little boy will be just fine. As has been indicated above, kids are really quite resilient. And not to be flippant, but, scars on boys are not such a bad thing. I have been a bit... OK, quite... accident prone all of my life, and I have the scars to prove it. In January I ripped open a nice laceration on my shin coming out of the water after a dive. Here's that one after we got back to the hotel and before I cleaned and dressed it:
It healed up pretty well. Hurt badly for a while, but, its fine, now. Big scar, but, fine, otherwise. I kicked a bike last week and have a similar-sized, but, V-shaped nasty gash on the back of my other leg now. I didn't photograph that one, but, its going to leave an impressive scar, too.
As a guy, I've never been disadvantaged by scars.
It is difficult to see your child in pain and frightened. But, you did really well. So did your boy, it seems! Good for both of you!