Has anybody heard of Botox causing permanent nerve damage?

I had Botox injections in my forehead over a year ago for a frown mark.  I had a severe heavy head immediately afterwards and this never actually went away.  I then developed a sinus infection, which subsequently took months to clear up.  Now 15 months later, I now suffer from facial pain, in my nose, across my cheekbones, behind my eyes, in my head and neck. Yes these sound typical of sinus problems, but I have had a CT scan and two MRI scans and all have come back clear so there are no problems with my sinuses.  The pain is almost constant and is totally unbearable.  My nose actually swells, as do my cheeks and my eyes go black underneath and my forehead feels tight and heavy.  I am convinced this has been caused by the Botox.  I never had any problems until after the injections.  I have been to so many doctors and have go no answers, yet I continue to be in constant pain.   One doctor I visited recently suspected it sounds like nerve damage caused by the Botox and I have now been referred to a pain clinic. If this is true, I am so worried that this is permanent damage that I could have for the rest of my life.  It is already runining my life since I am in pain 75% of the time. I am so scared and don't know what to do or where to go for help anymore.   Has anybody else ever experienced or heard of anything like this, e.g. Botox causing permanent nerve damage, hence constant facial pain?