My 16 month old started teething at 3.5 months and cut his last incisor about 2 weeks ago.

For a few days he has been off his food and had a runny bum.
Yesterday he started dribbling alot and last night was crying through the night in pain.
Today the dribbling continued but in excess, I've changed his top heaps, then when started screaming whilst eating I gave him a drink, calmed him down and got him to stick his tongue out (eventually!) where I saw little ulcers in a clump St the front side and a red raw patch in the middle and I think some ulcers a bit further back.

He only gas his big big ones at the back left to teethe, which I thought would be later on nearer two?

So my question is, do you think this is all related to teething? Or given that I think he should be done with teeth for now, should I get his tongue checked?

Could he be getting his big big ones seeing he was an early teether?
When did yours get the big back ones that are supposed to be at 2yrs?

Thanks