Hi there- paul is right...
I would also like to say if you can see this ulceration - it's on your tongue not base of tongue... (if it's base of tongue - then it's likely not visible to the human eye as your base of tongue is down your throat)
Normally an ulceration on the tongue is NOT HPV related - if it is cancerous it is generally HPV- cancer. This being the case there are two possibilities - 1) highly unlikely - a second primary - not unheard of - but very RARE or 2) spread from tonsil to tongue... Truthfully this is also highly unlikely - as normally from tonsil, you would get nodal involvement and possible base of tongue - someone will correct me if I am wrong here ... but to me that sounds rare as well.

So chances are good though not definite - that it's just an ulceration.
Ear pain? BIG TIME if there is an ulcer on your tongue. The tongue is very nervy... if the ulceration is deep enough and irritated enough it can cause ear pain. I know this from first hand experience.

Also Ear pain can be unrelated - I have noticed that my ear gets sore occasionally - why? every since my surgery/radiation I am rewired in there... So when I drink I some times get fluid in my ear canal... lucky ME! it's also a sinus issue...

Finally trouble swallowing... not unusual. Radiation not only causes ulcerations, inflammations, etc... it also causes fibrosis...and thinning of tissue. So your swallowing may feel tightened and difficult.

Finally - someone else replying said it best... chemo is not a cure. Likely if there is an issue / tumor, they may remove it surgically (particularly if it is on the oral tongue and visible) or they may do another round of rads/and chemo... which would be cisplatin or carboplatin.
hugs and best of luck and hopefully it's just a nasty ulcer.