You probably won't instantly regret it. You may never regret it. But you've got a lot of time between now and the rest of your life to see how it plays out and are free to gamble on the assumption of your own future perceptions.
I'm speaking from an element of personal evidence, so it should be taken as only that, but when I got a sleeve I could not imagine it bearing any relevance simply because I couldn't imagine at the time where I would ultimately end up in life and what I would ultimately begin to find important.
If I had stayed in the mindset I had when I got it, I'd still be there and the decision would never have changed. And my life would be just as static as it was back then.
But I changed. As did my social and professional circumstances. And those circumstances were not environments where visual indicators like tattoos actually provided value.
What did change were my ideas of what actually mattered to my context, leaving this expensive-as-fuck shit on my entire arm serving as nothing more than a permanent reminder of the fact that whatever I think I know about myself is subject to change.
That's the only value I get from it now. Maybe it's a blessing, but it doesn't stop others from only seeing a curse, and that's the downside. You can manage your own perceptions about things, but you can't manage those of others without hiding it.
And even though there are plenty justifications that sound something like "not caring what people think", let's face it... the only actual reason for a tattoo, much less a highly visible one, is for the sake of the perception of others. We can throw every justification at it and it still boils down to the singular fact that we ultimately did it for how it would be perceived by someone else.
Thing is, that's a double-edged sword.
So if I were to go back in time and approach myself sitting in that chair preparing for the first session, I'd tell him that he's fortunate.
I'd tell him that the reason he's fortunate isn't that I'm there to warn him of poor taste or not getting inked with something meaningful enough...
I'd tell him he's fortunate in that he would ever arrive at the realization of its lack of true value to begin with. Whether he went through with it or not.
But... maybe don't do it just to try and prove yourself wrong.