Small low-density lesion in left basal ganglia could be due to prior ischemia that the doctor never mentioned should i have this further investigated?

Yes- you should: Sometimes findings like this are made incidentally. It is surprising, but people may have these without any symptoms. While they are not normal, they can be benign if the follow up shows this was a small stroke and that all stroke risk factors (like smoking, blood pressure) are well accounted for and minimized.

Approach: First issue involves age and characteristics of lesion, as it may represent an archaic process unrelated to your current health. Secondly, a few blood tests and an EKG could determine your future stroke risk, and if problems are uncovered, pro-active steps could forestall future events.