Conclusion
When fingernail ridges occur due to aging, they are usually harmless and not an indication of any underlying condition. However, if your fingernail ridge is accompanied by other symptoms or changes in the mail, such as discoloration and bleeding underneath, then you should contact your doctor immediately. Your doctor will help conduct a proper diagnosis and treatment of any underlying condition, such as rheumatoid arthritis, peripheral vascular disease, diabetes, or thyroid disease, resulting in fingernail ridges.
Reference:
[1] https://my.clevelandclinic.org/health/diseases/17357-peripheral-artery-disease-pad
[2] https://www.nhs.uk/conditions/rheumatoid-arthritis/
[3] https://www.nhs.uk/conditions/raynauds/
[4] https://my.clevelandclinic.org/health/diseases/17689-kidney-failure
[5] https://celiac.org/about-celiac-disease/what-is-celiac-disease/
[6] https://my.clevelandclinic.org/health/diseases/10351-ulcerative-colitis