First of all, let me say something: holding the pen correctly will cause calluses. It won't hurt too much if you get calluses! Just bear with it and it will be fine. Relax when writing and it will slowly disappear. You can also use scissors to cut off part of the dead skin regularly (this is what I do, I have been doing this since I was a child practicing hard-pen calligraphy). But I think it doesn’t matter, the middle finger is not deformed, so there is nothing to worry about... Calluses are actually quite glorious, and it proves the hard work of writing~ Calluses are also helpful for calligraphy, as the calluses can support the pen barrel so that it does not slip. If you have any other questions, you can ask me~