I have a discolored rough patch of skin on my chest there is also a bump that i just noticed today on there. i am 19 years old. what could be causin?

Hard to say: Localized skin issues are generally due to localized contact with a triggering agent. Trauma, contact with a chemical, plant, cream, soap, etc. can give rise to a local reaction. It could be as simple as lemonade spilled on the site. A bump would suggest trauma or a bite. However, skin issues are very visual & without a better description or looking at it the cause is elusive.