I've recently noticed a red spot on middle of tongue, it's quite painful, anything to worry about?

Possibly. If the spot 'moves' (changes location) it is probably 'geographic tongue'...A benign condition. The red spot is a denuded area and it can be sensitive. Geographic tongue, also known as glossitis migrans, is usually intermittent in nature. However, it may be something else. You should have it examined by a dentist or oral surgeon trained in oral pathology.