Our daughter is 22 months old. She absolutely HATES getting her toenails clipped. If we ask, she immediately says no. If we try, she yanks her feet away and cries. We usually have to hold her down and just do it. Distractions don't really help either, she'll be totally distracted til we touch her feet, and she freaks out. Even just feeling her toenails to see how wicked they are will infuriate her.
She's not a big fan of having her feet touched in general, so we've been working on that, just lightly touching them, holding them, etc. It's helped somewhat in general touch, but she still hates getting them clipped.
We've never hurt her while clipping them, or clipped them too short, so I don't think it's a pain thing.