Chosen Solution

Help! I opened my iphone 6s and then there is a black dot on the bottom left of screen! I wanted to practice for my first time but did it on my phone like an idiot! How can I fix it without telling my mum or buying anything?

Sounds like you need to replace the screen, there is nothing to fix. You damaged the LCD. Sorry. You can get a good quality screen for about 30 dollars and if you want it fixed professionally it should cost about 75 dollars roughly. I would probably recommend you have someone at least help you out if it is your first time. AND ALWAYS DISCONNECT THE BATTERY BEFORE DISCONNECTING THE SCREEN CONNECTIONS.