Hi hannahgilliland,
Your
Fiddle Leaf Fig (Ficus lyrata) looks great! It would likely take quite a number of years for it to form a thicker trunk. As Fiddle Leaf Figs begin getting tall and leggy and lose thier lower leaves, they are usually pruned to force branching and a fuller plant but the best time to prune is probably late spring or summer and the cut stems can be rooted for additional plants. The side branch on your plant won't cause any issues with the tree gaining height or trunk size. Fall and winter months are when plants normally slow down in growth but once spring (and especially summer) get here again, your tree will likely really take off and put on more height.
