Well... I don't know anything about this. I'm not on Instagram or Facebook or much of anyplace else on the internet either. But I thought I would just say that, assuming this is someone you don't have a relationship with (you wrote you don't like him), I don't think there is any reason why you should allow him access to your Instagram site.

From my perspective, internet relationships can be tricky under the best of circumstances. So, in general, I would think it would probably be best to avoid having coworkers following you on the net. It's just too easy for misunderstandings that occur over the internet to spill over into one's work making everything just all that much more difficult.