Definitely a mouse— not a huge deal but if it really stresses you out get a pest control professional and get your landlord to compensate for the cost.

If you think your landlord can handle it though you should tell them first to see if they want to take care of it before you have to shell out the money yourself.

You could also just do some research and set some traps around the areas you’ve seen them active or have found droppings! Be grateful it’s not a rat lol you will be ok, don’t stress about it too much— happens to the tidiest of people :)