Probably nothing. ANA is a non-specific test seen in numerous illnesses as well as in healthy people. By itself, it has no prognostic significance except in juvenile idiopathic arthritis. It is a frequent incidental finding when broad work ups are done for non-specific symptoms.
It is not from IBS. + ANA can be present for a lot of reasons including connect tissue diseases, allergies, thyroid etc and you need to discuss this with your doctor.