Do you need sunscreen indoors? i heard even if the windows are open, you can just stay a few feet away from them to avoid needing to put on sunblock. it seems silly to wear it indoors, is it needed?

Only (maybe) if you have one of a few rare conditions that make you hyper-susceptible to sun exposure. If not and you are generally healthy, there is no need. On the other hand, if you're likely to be outdoors during the day, it makes sense to get in the habit of applying sunscreen automatically every day, especially if you have a light complexion and/or live in a high sunlight geographic area.

If you need sunscreen on a daily basis, have a pigment disorder or an autoimmune disorder like lupus, then sunscreen on a daily basis is a good idea rather than fearing to wander too close to a window open or not. Fluorescent light may be another source of UV. Find a moisturizer with sunscreen that is pleasant to use.