I have got a lump on my inner lips. possible symptom of oral cancer?

Doubtful: Ruptured salivary gland. Depending on how much it annoys you you should have it removed.

Rare to be: Cancer. More likely an irritation fibroma ( like a scar knot) from an injury or an irritated minor salivary gland with trapped secretions. Get your dentist or an oral surgeon to evaluate the lesion. Biopsy may be indicated but don't be too concerned.