swollen tongue

My DS2 has a sore and swollen tongue. So much so it is hanging out of his mouth and affecting his speech. He is off his food and drink as it hurts him and he was awake hourly last night cause it was sore.
He does have a throat infection as well at the moment, which doesnt help the whole mouth thing but the DR doesnt seem to think that his sore tongue would be anything to do with his throat.

I have had him at the doctors again this morning because I thought maybe it was thrush but nope not that. He had a good look around his mouth and tounge area and cant see anything (ulcers,bite marks etc) to be causing it so I have a miserable lisping boy who I cant help! :doh::wall:

I have just googled it and one possiblity is low iron. That would mean a blood test and me looking like a "Google Doctor Mum" :rolleyes:

Of course if he needs it then im all for it but thought I would check with the BB family first to see if in all their wisdom someone may have some answers for me

TIA