There is also a thing where blood vessels break under the surface of the skin and look red or brown. Sorry that I can't tell you more about that, but you might be able to find a photograph by googling.
First of all, let's rule out that this is dried blood. I assume it persists even through you having a bath or a shower?
My son got something in a similar area, the doctor named it right away but said it was a little unusual. My son got a prescription took it and it went away. I'm sorry but I can't remember what it was, but there was a risk to his liver or kidney and he had to have a follow-up test in 6 months to be sure there had been no ill effect. Just saying, it might be a good thing to find the money and see a doctor.
In some countries (Italy for example) pharmacists are very well trained. Possibly where you are, you could see a pharmacist instead. Wear a loose skirt or shorts that are loose in the leg (like rugby or soccer shorts) and just pull the leg up so the pharm can look. I only suggest this because my husband had to do that once for a rash on the chest when we were out of the country, and she prescribed the proper thing and he got better, and there was no charge for a doctor visit.