He's probably just a bit stressed and getting to know his new surroundings. You can try giving him some more hidey spots or some live plants; fish actually come out more if they know they have plenty of hiding spots available if need be. Also, putting some organic plain rooibos tea bags or Indian almond leaf in there (or just get some black water extract from fish store) can help decrease stress and aid good immune system. Tea bags you can get from health food section of grocery; just make sure organic rooibos ONLY ingredient. The almond leaves you can order online, but I found a readily available new source: go to hermit crab section (of at least one box store pet shop); they have the dried leaves in little sealed bags. Nice ones too and what I use for my guy; use for hermies to boost humidity and for tannins as well, just like for our guys. As long as your guy looks fine, no clamped fins, eating and swimming normally, I wouldn't worry. Keep up on water changes, watch water params closely and your guy should gradually get used to everything and come out more. Eventually he'll race TOWARD you when he sees you in the distance ;)
The more I think I know, the more I think I don't know much at all!