I do hope you are joking. Removing a lump from an animal is a procedure that can only be carried out by a qualified veterinary surgeon with anaesthetic. I have no doubt you will do more harm than good (both mentally to your dog and physically). There would be a high risk of uncontrolled, bleeding, skin break down and infection.
At home, you can certainly clean the lump with salty water twice a day in an attempt to get rid of the infection. You can also prevent scratching by using a loose cotton t-shirt that covers the lump. These two things alone may treat the infection as long as it is not too deep. If it is not resolving, antibiotics will be needed.
If the lump is a benign (non cancerous) growth such as a cyst/skin tag etc., at her age most vets would likely take a wait and see approach and not remove it anyway. They would check it every so often to ensure it is not growing or changing and treat any infections that may occur.
If it is a cancer, it would typically need to be analysed before removing it. This is because certain cancers, such as mast cell tumours, can grow deeper than expected so just removing the portion of the lump that is visible won't actually do much good.
Again, please do not be tempted to perform any sort of cutting/removing yourself as you are more likely to create a problem rather than fix one.