Just handle them regularly and remember to not put them down or back in cage if they do bite, as that reinforces their idea of 'bite = get put down'. Though BTSs being so friendly, I can't picture that as the cause for nipping. Maybe they just want to test you and see who's really the boss?

At any rate, have fun with the little one, and over time they should calm down.

Oh, and DMTWI - Nice fella you have there!

This is my sweet IJ fella, Topaz.