What is the ruling on performing the ritual bath (ghusl) and repeating the prayers if there was a barrier on part of the chest during the post-menstrual ghusl, and this was discovered hours after the ghusl and after performing some prayers?

One should be wary of obsessive doubt by ignoring it and not paying attention to it. The barrier that affects the validity of purification is a tangible substance that prevents water from reaching the skin. For the full body ablution (ghusl), the predominance of doubt is sufficient, and doubt after completion does not have an effect. The nipple and its tip are exposed areas where water can easily reach, and their contraction is not deep enough to prevent water access. A minor barrier on the body is excused, such as slight dirt, blood, dough, and the like.