I have a crusty mole on my shoulder. should i worry?

Get it checked: If this is a mole you have had for a while that has now turned crusty, then it could be concerning. What you are describing also sounds like a seborrheic keratosis which is usually not a worry. However, It could be a number of things concerning and non concerning. I would recommend you get in and have it looked at.

See a dermatologist: Change in a mole should prompt a visit to a dermatologist for examination.

See a dermatologist: The only way to ensure you have nothing to worry about is for a physician to see the mole. Then they can determine if you need a biopsy.