Probably.  Get it checked out.

    Check the spelling: it's mucocoele.  Yes, this sounds like a mucocoele.
 They're very common on the lower lip.  They are generally caused by
trauma (ie: biting) of the minor salivary glands that line the inside of
the lower lip.  If the duct is damaged, the secretions build up under
the tissue until the tissue ruptures.  Usually they eventually resolve
on their own (at least the ones I've gotten have) though they
occasionally have to be removed, which is a pretty easy procedure that
is simple and only mildly annoying.
    The larger so-called mucous retention cysts, esp. those in the floor of
the mouth called "ranula" are a bit more involved, but basically
treatment is along the same lines--surgical removal.

Steve