There is always a slight increase in sensitivity after gum treatment. You must complete the treatment else it will go on damaging your gums and bone support of your teeth. Sensitivity can be controlled by sensitivity toothpastes and mouthwashes. If it is too much you can ask your doctor for specific treatments like varnish available to reduce sensitivity

Dear concerned, Do not get demotivated with treatment options. After cleaning little sensitivity is expected and you might have visited your dentist after few years for cleaning. You can apply metrogyl gel, but visit your dentist. Explain you are not interested in cleaning. If there is puss coming out it should not be neglected.