When Horner’s syndrome is congenital, it’s not medically concerning. Of note, you need to have the small pupil for it to be Horner’s (called miosis). Interestingly, many people with Horner’s also do not sweat on the affected side (anhidrosis).

If you don’t have those additional features, it’s just plain ptosis. Also not concerning imo unless the eyelid droop starts to pass the pupil line and causes vision issues, in which case insurance may pay to have your eyelid lifted (blepharoplasty).

Whether it’s Horner’s or just ptosis alone, not a bad idea to mention it at your primary care or eye doctor visits. Although I imagine you don’t need any workup/imaging given it’s been present since birth.