According to the Unfinished Tales, Gimli was forbidden to join the quest company for being too young (62), so he was probably not old enough for war either (oddly, his father was present in the Battle of Azanulbizar when he was only 16...). Also, Gimli probably resided in Thorin's Halls in the Ered Luin during the Erebor quest, far away from the Lonely Mountain: only the dwarves in the Iron Hills were close enough to join the battle.
In the Hobbit book itself, there is certainly no mention of Gimli since he did not yet exist when it was written
__________________ Life is complex: it has both real and imaginary components.
Ya I know there was no mention of him in the Hobbit for obvious reason as you stated and i also knew the age of his father during the Battle of Azanulbizar which is why I asked. I just didnt know if there was some small hint or passage somewhere that mentioned what he was doing at the time.