To take care of head is to literally "take care" of your own personal head, specifically by usage of drugs.
Originally used in 1980 by the band The Toyes in the song Smoke Two Joints, the phrase became mainstream popularized when Sublime covered it in their album 40 Oz. to Heaven 16 years later.
Masturbation primarily for maintenance and not necessarily for self gratification. Without it, one may not think clearly, act rationally, or make the best decisions around the opposite sex.
Much like clearing bats out of the belfry.
Brian: I screwed up last night with Karen. I was off my game.
Simon: 'Cause you weren't thinking dude, all you wanted was to get laid.
Brian: Huh. Really?
Simon: Next time, take care of business before seeing Karen.
It usually means you don't want to go and do something, but alternatively it can also means you have the shits and you're too embarrassed/professional to say it.
What a man says when he acts like he really be doing everything by going to work and paying a bill or two but actually don't take care of a damn thing at home including his woman, fixing shit, yard work or chores. He actually don't take care of home at all. He just feels that way.