Ok my baby is a year old and he has a hard plastic tiki cup that I bought at the local $ store that he likes to get in and sleep but he mostly likes to sit in it and (sounds) like he is just scraping his teeth on it, it's like the nails on a chalkboard sound. Ive never seen him doing it he just wakes me up at night with the sound and you can see the marks on the cup. Is this ok/normal or should I have him checked out.

Yes, it's normal. My girls had chewed the heck out of their wheel wheel that they came with to my home, after giving them a toy bin with hard plastic objects for them to chew on, they had chewed less on their new wheel. All their wheels had/ have some scraping marks, what I call "testing" but none are chewed as severely. They have also been in mesh enclosures for temporary living on occasions and never attempted to chew through, so I know they're not excessive chewers. But some do chew more than others.