Are the dryer sheets unused? I think I would first call the pediatrician and see what they think. My son eats wipes all the time, or at least sucks all the juice out of them... (not something I allow him to do by the way, they have a way of sneaking them) I don't see this being a serious problem... My guess is that this is a little more common than you'd think. If you need the peace of mind call you ped. and get some answers.

Also, any time your son ingests something that you are not sure about, call poison control. You can tell them what he ate and they can tell you right away if it's something to be concerned about or not. I called the other day when my 3yr old ate a cough drop and even though I felt silly It helped that it was on the phone so they couldn't see my red face :)
I remember when my 10 yr old was 2 & 3 she would eat anything she picked up off the ground, even if she didn't know what it was. And she went through the dirt-eating phase. Now it's funny but then, not so much!

I know children learn through exploration, by touching, tasting..etc. but you would think a dryer sheet would taste nasty...lol. Anyway, try looking on the box that they came in and see if it has any type of warning on there like other household products. If it doesn't, like MellisaB suggested, call poison control. They definetly eased my mind when I had to call them a couple of months ago because one of my girls knocked over a lamp and broke an energy saving lightbulb. I heard on the news that they were full of mercury and that you should immediatley evacuate the house should one break and blah, blah blah. Well, as the news always does they exagerated and the lady I spoke to at poison control helped me through it. Good luck with your little taste tester:)