Sorry to hear being stuck to the couch! Good though that you've still got the passion to keep playing with the camera even in tight confines and limited scenes.
Experimenting with M mode and getting to know the flash are two great ideas. I'd also consider learning all of the camera's features and how they work. Play with the HDR mode to understand first highlight exposure and second shadow exposure, and with the manual settings how much to set the exposure value between them at. Maybe do some depth of field experiments with big apertures vs small to see how your lenses perform. Might be a good time to try some still/macro type shooting on small subjects around the house, especially with the shallow DOF - blurring background on tiny objects with shallow DOF to hide the fact that it's indoors - and also creating the illusion of the object being bigger than it is. Some high ISO work could be fun - since you're in dark environments indoors - try finding the sweet spot between proper exposure and ISO - it'll help illustrate how noise is not only related to high ISO, but moreso to underexposure in high ISO - sometimes a properly exposed ISO3200 can have less noise than an underexposed ISO1600. And I'd suggest experimenting with ISO6400 and ISO12800 using the HDR mode - it's a revelation! Set the HDR to +1 (the minimum setting), then take some shots at the highest ISO settings - compare these to taking a straight ISO6400 or ISO12800 shot without HDR. It really shows you how the image stacking of the HDR has a great side effect of significantly reducing noise and restoring detail...and making those very high ISOs actually usable.
Sony DSLR-A68 / Sony 18-250mm / Minolta 50mm F1.7 / Tamron 150-600mm / Minolta 300mm F4 APO
Sony A6300 / 18-55mm F3.5-5.6 / 55-210mm F4-6.3 / 10-18mm F4 / 35mm F1.8 / 16mm F2.8 / FE70-200mm F4 G OSS / FE70-300mm F4.5-5.6 G OSS / via manual adapter, lots of Pentax K mount, Konica K/AR mount, and Leica M mount manual lenses