If you are not confident about your roof and think your roofing system was installed incorrectly, it’s always best to schedule a roofing inspection with professional roofing contractors.
If your roof has a problem similar to the photo above. Then it’s a case of a low-hanging nail. More importantly, an exposed nail in the butt ends of your shingle application, in the path of water.
It may not be an immediate issue but may lead to cause serious roofing issues if not dealt with sooner.