The buzz is really quiet but i'm just wondering if it is normal or if my Bass has a grounding problem?
Yep, ground problem.
It only does it when the tone is up, before I got the bass the guy showed me it and it didn't have any problems but after that he said the tone knob was loose so he said he tightened it. Could he of messed up a wire connecting to the tone?
It could be a loose connection or bad grounding. You could get someone who knows about electronics to open it up and have a look. Is it a cheap bass? Ive found most cheap bass/guitars to have similar problems.
Sometimes you can get hissing from basses when you have the tone all the way up. I think it has to do with the high frequencies randomly around. Is it a buzz, or more of a hiss?
Beside grounding are you playing too close to a computer/TV or fluorescent light fixture
Should I get the shop I bought it from to fix it since its on a 1 year warranty?
Two single coil pickups will hum unless they're balanced properly, which means adjusting their individual volumes until the hum stops. However, that may not be applicable. What bass are you playing?
It's quite possible that your amp, or even your house, is the one with the grounding problem, not your bass. I've noticed that my main bass has that exact problem when I play at my church and in my room at home, but when I play in the main room of my house or at college it's dead silent.