W2 for state I didn't live

So I'm Self Employed living in California. I'm software developer so I have clients all over the states and usually receive 1099. 

Recently, I received a W2 from client that is in Colorado ( Expected 1099 ). Even more, I have paid CO tax on that income. The amount is $420.

 

My question is, how do I handle that in Turbotax Self Employed? I never lived and don't have any sort of income from CO state, besides this weird W2. I talked with client so we handled this situation going forward, however he filed 2019 already. How do i handle this situation?