For the last two weeks I've been experiencing mild discomfort in the rectal area. Yesterday I took a photo of the anal area to see what's going on. I noticed a small lump that is darker than the skin around it. Is this external hemorrhoid?
The skin around it has a slightly more red color. It is painless when touched, it's also rather undetectable with finger.

Photo: https://imgur.com/a/jw0ju7g
I'm wondering whether to go to the doctor. Please advise. Thank you!

I advise you go see a doctor soon. Do not take these things lightly, the faster you find out what it is the more chances you have not to end up with something more serious.
Good luck!