Yes sure, it is the presence of mold. But it must be removed before it will grow in larger one.
Here are few steps to remove them
Prepare a solution of chlorine bleach & water :-
By taking one part bleach to 3 parts water – or get hold of a household detergent like Domestos bleach spray with bleach as an active ingredient.
Using a stiff-bristled brush, scrub the infected area. Rinse thoroughly and dry.