If it were me, I would keep it. But since you didn't mention what denomination the note is, I can't tell you more than that.
I'd keep it, but right now it probably isn't worth more than $3 or $4 in CU condition, unless you can find someone itching for a low serial numbered two. But like I said, I would hold on to it for a few years, and it'll keep going up in price, especially if you keep it CU.