Haha yeah. My friends nails are long and she tickled me this one time and it seemed like she was tickling me with razor blades. She slowed down a bit and was slowly tickling me and gliding her nails against me so that helpled a bit lol. Some people do have really long nails and when they tickle you really fast it can hurt a bit...it sucks lol.
Depends on how long their nails are and the type of tickling they are employing on you, I suppose. Soft, and gentle tickles are usually are what nails are made for, but if they try to get more 'vigorous' it can really hurt!