Chances is there are tension on the Procerus muscle. Unknowingly, you might have sit off balance, slightly lean to the front which is mostly cause by both/either one:
i) breath in and breath out not balance; check that and try to purposely control the breath to be balanced for while before letting go the controlling part.
ii) too much energy, strong viriya, ‘chasing after’ the breath. Causing tension even when you sit spinal straight.
The Procerus muscle is the pyramid-shaped muscle extending from the lower part of the nasal bone to the middle area in the forehead between the eyebrows. I suspect the Transversus Nasalis muscle may play a part that influence the pain to be felt only from the middle of the nasal bone to the middle area in the forehead between the eyebrows.
Sharing with you what I picked up from a meditation teacher:
Put your palms together right in front of your face, thumb touching your nose with eye open. Open up your palms to the side, both sides about 8 inches; total about 16 inches (distance is only a reference). Hold it 1 minute and know your two palms simultaneously; NOT with your eyes!
Put down your hand; repeat a few times. Now raise both palm directly open a few times, know the space not your palm; know it, DO NOT bother much on the distance.
Close your eye and start sitting. Sit for a while, relax. Raise your palms direct open and know the ‘space’ for a while. Put down your hand and maintain knowing that space for a while.
Let your muscles relax completely, maintain your consciousness within that ‘space’ and start paying attention to your primary meditation object, the breath.
If you do try this method; after sitting, try to reflect back the differences between your original practices from this practice; what’s the different in “knowing” the breath. Perhaps you can figure out what is meant by other posters on strong energy (viriya).
Btw, if the pain comes very soon when you sit right after you bathe; compare to not taking bath, then what you suspect of meditation amplifying the sensation may not be just a doubt. Anyway, the above method still can help in this case.