New feeling in fj

So last night my (f) 29 was messing around well in time she was giving me a fj. And then I feel something that felt odd but nice. She was pushing her toenails into my shaft. It was a little painful but very nice feeling she didn’t scratch or tear anything just kinda dog them into my shaft oh man was the release soo intense and powerful.
I ask has anyone have this or lady’s have you done this. What did it feel like for you or am I the only one !?