Hi, I can understand your concern for bumps on back of neck, face and on right side of mouth. The history provided is too brief but I can make a probable diagnosis of Herpes zoster or shingles. its sudden appearance, pain, deep redness and further spread to the chest and shoulder area in 4-5 days of period. It is not unusual to find such kind of picture in zoster with red areas and pain present on one side of body not crossing the mid-line. I suggest you to take a painkiller tablet such as paracetamol by mouth for two times a day after meals. This will reduce the pain intensity and if pain persists then you can take it for 3 times at a gap of 8 hours. For the itching part antihistamine tablet such as Loratadine (Claritin or lorfast) would be most appropriate to be taken in the same manner as for paracetamol. Oral antiviral may be required such as acyclovir for best coverage of the problem. If your symptoms are not matching above then you need to take second opinion and accordingly go for the investigations suggested by the doctor.