As you say you are a smoker and you saw a lump type swelling on the hard palate
. it can be due to many reasons like you might have tooth abscess
which is reflecting on palate, it can also be condition called mucocele
(due to blocked salivary glands) . There can also be a growth in Maxillary sinus which shows off as a lump on your hard palate.
Do not ignore it.Just take an appointment from your dental surgeon first. your dentist
might give a better idea about it.