Can you do a skin biopsy for lupus with no rash and it be positive for lupus?

Possible: Would require getting a location that has the characteristics of lupus on examination. Not sure of the odds, but it would be possible.

Yes: There is a condition called discoid lupus where patients have scarring, especially on their scalp. There is also a condition called subacute cutaneous lupus. Also, biopsy reports can be "consistent with" lupus but sometimes findings are non-specific. Ideally you should see a rheumatologist to sort this out.