How did you get injured?
Also did you undergo an X ray or ultrasound of the injured part of your back?
It is possible that the bump in the back is a hematoma due to back injury.
I would suggest you to please get an X ray or a CT scan of the injured part to rule out any nerve injury.
The cold sensations could be because of a past viral infection or even due to peripheral neuropathy.
Please schedule an appointment with a physician and undergo a complete neurological exam. Do keep us posted!
I too was told by a doctor that I have a upper back sprain, strain. It to was a severe pain in my shoulder area. He give me muscle relaxers and pain killers and told me if in two weeks it was not better to come back for more tests. It subsided for a couple of days and now is my arm is in severe pain. I have sharp pains in my neck that migrate or immediately radiate into my wrist. Almost feels as if my arm is broken. Also my right index finger has been numb from day one with no sign of recovery. I have absolutely no strength left in this arm. I can barely hold my arm up. Also, I cannot lie down in a bed. Just to painful... Of course, I have no insurance and cannot afford to go to a specialist. All the while, I have still been working and yes my job consists of having to sometimes pickup extremely heavy product.