The 2 bumps you got is doubtful weather it is of scabies
Generally scabies is common on the skin between the fingers,having very small eruptions and there is lots of itching and sometimes due to severe itching
there is infection.
So you should be confirmed scabies,there may be scabies on shoulder but primarily lesion is in between the fingers.
so let it be diagnosed by dermatologist
ok and bye.