The dryness and shape of the mark suggests that this is most likely a type of ringworm (tinea) that affects different places on the body and is not a threat to your immediate health. This can appear as a red mark or it can appear slightly lighter in color than the skin tone as you have described. Over the counter anti-fungal creams are very effective on this type of infection as is keeping the area dry and avoiding irritation such as scented soaps, etc.
I hope this is helpful to you; please remember to press ACCEPT and feel free to contact me if you have anything to add.
Please remember to press ACCEPT so that I may be compensated by the website for my efforts. Positive feedback is much appreciated; please remember that this feedback is personal to me and not to the website, thank you!