Welcome to HCM.
Understanding your concern.
Thanks for your query . The bumps you mention on the back of your tongue are tongue papillae which are larger in size at the back of the tongue as compared to the front part of the tongue .
These papillae are present in 'v' shape pattern at the back of the tongue and in some people appear as if they are inflamed , but they are totally normal . You also mention in query that they are painless this also confirm that these are normal.
I would suggest you to observe them if they grow in size with time or the change their color or they taste different or getting painful , then it will be cause of concern .
These white bumps can be inflammation of these papillae because of infection , continues irritation or trauma ,lie bumps ,oral thrush
or cancer type of condition (rare possibility).
The medicine you mention is amoxicillin
which can also be the reason for tongue allergy
as a side effect. So get your change by consulting your doctor .
Then you should consult oral pathologist for proper diagnosis . Doctor will examine then physically and order biopsy
to confirm the diagnosis and treat it accordingly .
For now maintain proper oral hygiene
,brush and floss twice a day , clean your tongue properly and do antiseptic mouthwash rinses (listrine)
Hope your concern has been resolved.
Get Well Soon.
Dr. Harry Maheshwari