Am I stuck with just a min-raise here?

[SpleenLSD]

1-2NL max 100 buy-in at a FL dawg track. I'm making a note about a cooler of a hand from 3 hands ago when I come to in the CO with 2 black kings. I announce raise and throw in 12, not realizing UTG limped, UTG+1 raised to 12 and MP called. So if I had actually been paying attention and not steaming I woulda popped to 30ish. Dealer stops the action, points out the raise ahead of me and said the raise is to 18. I asked if I was permitted to raise to more than the minimum and was told I was stuck with the min raise. Standard? At that moment I was like Donnie in The Big Lebowski, completely clueless, so I didn't push the issue.

To add a results-oriented footnote an Ace flopped and the two players in front of me shoved and called so I released saving me $12-15 which I was generous enough to donate to someone else on the next hand.