I live in Massachusetts and recieved a 1099k form from StubHub

Yes, you do need tp report this as Self-Employment income.  You can claim your expenses and losses against the income but you do need to report it using Turbo Tax Self-Employed. 

Please use the following steps as outlined in this Turbo Tax link , to enter your income and expenses from your 1099K.  For clarification, i have added some additional steps.

• Go to Federal > Income & Expenses
• Scroll down to See all income. In the Self-employment section, click Start next to Income & Expenses
• Answer Yes to Did you have any self-employment income or expenses?
• Continue through the interview to enter your business information. Even though you don't think of this as a business, it is reported as a business for income tax purposes.
• When you get to the Let's Review Your Work Info screen, make sure everything is correct and then click Looks Good
• On the Let's get income for work screen, select the type of income you want to enter and click Continue.
• When you get to income section where it asks you your income, you will make the selection that this is other common income (1099K etc) This is where you enter your 1099K information.
• Proceed through the rest of the interview to enter your income
• After you are done entering income.  You will begin entering your expenses, including your losses.  Turbo Tax does a bery good job guiding you through this section.
• Have a great tax season. 

Thanks, I submit it my taxes already because I didn't know I would get one of these. What should I do if my taxes have been accepted?

You will need to amend your return.

 To Amend in TurboTax:

 

• Sign in to TurboTax.
• Scroll down to Your tax return & documents (you may need to select Show), select 2019 and then Amend (change) return.

• If you only see the option to amend 2018 or earlier, it's because you can't amend an unfiled 2019 return. Instead, just select Pick up where you left off, make your changes, and disregard the rest of these instructions.

• Select Amend using TurboTax Online.
• Carefully follow the instructions. Don't worry if your refund changes to $0. This is normal on amended returns.
• When finished, we'll give you instructions for printing and mailing your amended return as amendments can't be e-filed.

Three weeks after mailing your amended return, you can start tracking it at the IRS Where's My Amended Return? tracking tool.  Please allow at least 16 weeks for the IRS to process your amended return.

It says amending on turbotax is not available until late February, I already filed my taxes last week so I'm trying to figure it out.

You can start the amendment after the form is available. Form 1040X, Amended U.S. Individual Income Tax Return will be available on 02/12/2020.