ULH,
At your stage, especially on your first solo, choosing NOT to fly was absolutely correct. With a bit more time and experience behind you you will be better able to exercise judgement on matters like this, but even then, if you are at your home base airfield there wouldn't be many compelling reasons to take to the air with a known defect like this.
As others have said, a lot comes down to the aircraft type. My own aeroplane is a (permit to fly) light tailwheeler with heel brakes which are generally only used during the engine run up, but are sometimes need to turn when taxying in strong winds. I was once away from base about to fly back to home when one of the brakes failed on taxy out. I taxied back, shut down and investigated. Suffice to stay that after a lot of consideration and detailed planning, I flew back with one brake inop, to base where I could get the snag rectified. It was not a decision taken lightly and this was one of the few occasions when I would carry a defect like this. At the other end of the scale, in my work aeroplane, you probably wouldn't even remove the chocks with a single brake failure!
On this note, on GA types which do not have a Minimum Equipment List, is there any guidance as to what snags you can legally accept and which ones will ground you - or does it simply come down to individual judgement, airmanship and common sense?