It’s possible something else is wrong with that vial of gear like too much solvent, but I 100% guarantee it’s not because it’s two years old. The expiration date on medication is complete bullshit. There’s been studies on it. At most is loses some potency.
I never got PIP until one day I did and even had some redness near the site. It happens.
If you’re that concerned then trash it and order something new
Not true for all meds. Doxycycline, a common antibiotic, degrades into toxic liver destroying shit after a while, without any visible signs or oder.