My newborn of 8weeks has a thumb nail that is split half way down his thumb nail and brown discoloration. it looks like it's grown funny? what is it??

The most likely : cause would be unrecognized trauma, especially if it appeared recently. Brown discoloration is usually from bleeding under the nail. Show it to his pediatrician at his 2-month health maintenance visit, just to make sure it's not from something more serious. You may want to photograph the lesion every couple of weeks so his doctor can monitor its healing over the next few months.

Shd be seen : There is no way to give a diagnosis as well as any guidance without seeing the child and the nail in question. If very worried u shd have him seen right away. If the baby is fine, feeding well, sleeping well for his age and there are no other concerns then u can ask his pediatrician on ur next visit to the doctors.