Certified GKH Gardening Expert
Yes. I see, what looks like, a trunk originating from below the graft union. Essentially, what you have is a wild citrus that is likely much taller than the grafted one. Anything coming out of the ground that is NOT the large, main stalk should be removed. Anything that is not located above the graft union will be a wild citrus. Effectively, this sucker impedes the grafted top and its production.
Here are some articles that will help: