Slight pressure/discomfort on back left side of head last few days. feels like i need to stretch it out. should i be concerned?

Probably not: Feel the skin over your head back there & see if you can find the source of the discomfort. It may be a swollen lymph node or even a pimple or small abscess. If you find something like that, it will probably go away on its own. If not, or if symptoms persist/worsen, go to Urgent Care

Ache: No it sounds as if it's probably his musculoskeletal and is of no consequence