Yes! If you mean a plastic or wooden ring around the trunk from a plant tag then cut it off so it does not girdle the tree. I could not see a ring in the photo. But if you mean a bump on the bark that is part of the trunk then that "ring" could be the scar tissue from a graft union. This is when the roots of a hardier lemon are grafted or joined to the top of a lemon variety that has better taste. In this case the ring can be ignored as it is part of the plant. Hope this helps, Keep growing, Marianne Binetti ,