Thanks for your query .
The boy is probably having oral thrush
a common fungal infection
Can use mycostatin
oral suspension 1 ml 4 times a day for local tongue application.
For fever you can use panadol in appropriate doses .
If there is no improvement in 48 hrs or so please get him checked by your GP.
Also keep him well hydrated by giving frequent cold
liquids & feeds as usual.
Hope you find the information useful