If Earth is closer to the Sun in winter (January), why is it so cold in our Northern hemisphere in January?

It's probably because the earth is actually tilted and is not straight when orbiting the sun. That's why when it's winter here, it's summer in the southern hemisphere. In the wintertime in the northern hemisphere, it's colder here because it's tilted away from the sun and the southern hemisphere is tilted closer to the sun (I believe this is the case anyways)

The northern hemisphere is further away from the sun