I Have Blister Or Ulcer Like Spots On My Tongue

I have blister or ulcer like spots on my tongue some large ones and some tiny ones barely visable..the bigger ones have like a tiny red dot in the middle like the mark an injection would leave! They only come in the evening time and are quite painful,can you advise me on home remedies or do you have any idea what it is or what's causing it? Could I be allergic to something even tho my diet has not changed!