Don't want to scare you, but helmets don't do much to prevent the brain from injuring itself against the skull (think of your helmet like a crumple zone on a car; it helps, but without a seatbelt you can still smash yourself against the steering column or whatever, where you=brain and steering column=skull). It's been pretty well established that helmets can't prevent concussions (just ask the NFL, or more specifically, their sports medicine doctors and experts; also look to the military and their doctors and risk reduction experts), but if you're feeling better then you're probably in the clear.

It's a good sign that you can remember the crash clearly, as memory loss is a pretty solid indicator of brain injury. It might not be the worst idea to have someone check on you throughout the night, just to make sure that you're still breathing, if that's possible. But again, the fact that your pain is going down is a really good indicator that any brain injury you might have suffered is negligible, or even non-existant. At least that's what they taught when I was an EMT/ski patroller (and yes, we saw a lot of head injuries, mostly from the terrain parks, many wearing helmets, and helicoptered a lot of them out).

If the pain persists or gets worse, do go to a hospital. If you have insurance, there's really no reason not to.