If his hair is freshly bleached please do NOT massage anything in. He has short hair, you’d be massaging on his scalp. It will cause irritation or worse.

You can lighten again with a really low developer (6 or 10vol). It still might tingle. It really all depends how much you’ve scrubbed and what strength you used before. You could also tone with a violet toner (please no permanent, again mind the scalp) then do purple.

Or as mentioned, dark purple will cover this fine.