Well that's a relief.
My dh had the same, I would guess. He had an acoustic neuroma, or more correctly, a vestibular schwannoma.
His 2nd MRI, a year after diagnosis, showed it had grown a smidge (I actually think they just measured it more accurately) so he decided to get it dealt with.
We had 3 options - surgery, stereotactic radiotherapy or gamma knife radiosurgery.
After much research he opted for option 3. He was treated at The Cromwell in London, in and out in one day and back to work the following day.
The only side effect has been that he has lost his mid-range hearing in that ear as a consequence of the radiation (in the US, they give you 3 months of steroid treatment after the op to avoid this, but it's not protocol here).
Having said all that - I think the vast majority of people with acoustic neuromas do nothing at all as generally, they don't grow.
Hope yours is a non-grower, but even if you need treatment - it's no big deal!