No one I would feel safe piercing my tongue would pierce your tongue. Why? Because it is illegal and that person could face prosecution. It is illegal for several reasons, but the most important is that it is life threatening if done improperly. I would not trust anyone willing to break the law to be following other "rules" necessary to keep you safe.
Now you do know that it takes three weeks for a tongue piercing to heal? You have to gargle frequently and eat soft food.
And it might even be longer before having fellatio would be comfortable with anything in your tongue that MIGHT actually make a difference to how it feels to him.
You also need to consider not only what impact your tongue piercing has on him, but also on your teeth. Dentists do not have much positive to say about metal tongue jewelry.
Research is starting to demonstrate a possibility that some forms of hepatitis is more common among people with tongue piercings. STDs of any kind are more easily passed between two people when one has a tongue piercing (that IS fact.)
Recommendations I have read say you should not KISS anyone for eight weeks after having your tongue pierced.
Is all this really worth the POSSIBILITY that sex might be better?
If you read online you will see plenty of guys who have said it made no difference - other think it is great. The guys who think it is great seem to think that its makes a woman/ man great at giving oral sex better - but if she/ he is not good already - it doesn't do much.
Personally I think you just have to accept that the price to pay for keeping absolutely safe from disease is not the greatest sex in the world and you have that to look forward to in your future. Improve your sexual technique. Use sex toys, lubrication, and ambiance to make things better. Try new positions. There is a ton of things to do without having a piercing done.
Susan