mouth sensitivity

I had a tooth abscess about 2 months ago and had it pulled right away (a difficult extraction). About a month later, I returned to the dentist to have a filling in the tooth beside the one that was pulled. When the dentist inserted the needle to freeze it, the needle ripped my cheek. Both the dentist and I were surprised. He put in 2 stitches, and completed the filling. My cheek was a bit swollen, but I thought that it was just from pulling on my cheek from the filling (the filling was in a back tooth). The swelling and pain got progressively worse that day and into the evening until I could not stand it. I called the dentist. His son, also a dentist in the same office, called back. He thought that I was developing an infection, called in pain medication and antibiotics to the pharmacy. When I went in to see the dentist the next morning, he was surprised by the degree of swelling I had. He gave me steroids and stronger antibiotics. Things resolved very nicely. I have been trying to figure out what went wrong. At first I thought that this all happened because my mouth was not healed from having the tooth pulled. Finally, I remembered the dentist giving me some toothpaste samples to try. After using it, I had extreme sensitivity in my mouth, gums and even my tongue. I discovered this when I tried to eat some mild salsa. My entire mouth was on fire. My mother said that it was not really hot at all. I stopped using the toothpaste about 6 weeks ago, but my mouth is still sensitive, even to oil and vinegar salad dressing. What can I do?