What is the ruling regarding my prayer and purity after discovering remnants of clear nail polish on my nails, and am I obligated to repeat past prayers? And is this considered a minor, excusable matter?

Nail polish (manicure) is considered a barrier that prevents water from reaching the skin, so ablution (wudu') is not valid with it if it has a physical mass. However, if it is merely a color that does not prevent water from reaching the skin, then ablution is valid with it, similar to henna. Some scholars have been lenient regarding a slight barrier that prevents water from reaching the skin, such as Shaykh al-Islam Ibn Taymiyyah, and they based their view on the principle that "hardship brings ease." If a person doubts whether it is slight or substantial, they should treat it as slight. However, if the polish is substantial in the person's belief and acts as a barrier, they must repeat the prayers they performed before removing the barrier and continue to make up for them until they are reasonably certain of having cleared their obligation.