Actually, in practice, the most helpful initial information, beyond the history, for the physician is simply identifying the physical character of the "bump". To the doctor, when the patient says "bump" it signifies only a localized elevation of the skin. There are many skin conditions which would cause the skin to be elevated. For the doctor, the color,surface texture, depth within the skin, softness or hardness, mobility, tenderness or itching to touch, tendency to weep or drain, ulceration, distribution pattern and other characteristics of the "bump" may suggest possible diagnoses. These possible diagnoses would then often suggest whether or not external factors need to be investigated. For a non-doctor to get an idea of what disorders are related to what appearance of the "bump", you might want to go to the Merck Description of Skin Lesions:
http://www.merck.com/mmpe/sec10/ch109/ch109b.html
My point to be made in this Answer is that the specific appearance of the "bump" can set the stage for a diagnosis and treatment and possibly understanding which causes are important to attempt to eliminate or change. All uncertain and symptomatic "bumps" should be evaluated by a physician.. ..Maurice.