itchless painless sore on penile shaft
Regarding a genital lesion
Hello and welcome to ask a doctor service. I have viewed the image and gone through the query.
Could be either a herpes blister or an early wart. I suggest you to use a topical antibiotic e.g either Neosporin ointment or Mupirocin ointment for a week. I would suggest a screening test for genital herpes after 8-12 weeks from your last sexual encounter. Herpes infection can be clinically silent therefore this might be a manifestation of a past infection. HPV can be considered if it doesn't resolve or becomes raised. In that case it had to be either fulgurated or freezed with liquid Nitrogen.
Hope I have answered your query. Let me know if you need any more assistance.
Regarding genital ulcer
STD tests need to be interpreted in a time bound manner. If you did them more than 12 weeks after your last risk exposure then they are certainly conclusive. Otherwise, if done too soon they may be falsely negative. Can you sent a recent photo? How has it changed or evolved now?
Let me know if you need any more assistance