If the brush was a steel brush, it's possible (but quite unlikely) that the barrel could have been scratched. Even if that happened, it's very unlikely that it would affect your accuracy to any noticeable extent nor cause any other significantly negative consequences.
If the brush was bronze/brass or nylon then it didn't do any damage.
The best ways to avoid getting a brush stuck are to use a properly fitting brush and to not change the direction of the brush while it is still in the bore. In other words, push it all the way through so all the bristles are out of the bore before you reverse direction and pull it back.