Ah, the "shed some light" paragraph certainly did. And the difference between the initial asking at 15 (with flip-flop) and now at 20 is considerable. So, all told, given your situation, I'd probably just go do it and don't mention it, and don't take pains to hide it or show it off. Making sure the tattoo place is sanitary and licensed and blah blah blah first would be good, of course...
On a personal note, I don't like tattoos. It's not a big OMG reaction, and I can understand them, and can toy with the idea of getting one. It's just not my thing. (Maybe it's the permanence I don't like?) However, piercings REALLY turn me off, and not just from a parent's perpective. Shudder.

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