Lava would give off light but I don't think it would light up much space. I would give it a 10' radius or so.
It's actually up to the GM, because not all lava is equal. Even flowing lava can have a completely opaque black crust on top, shedding no light or negligible light along cracks. For 'normal' lava, I'd say regular light out to 5ft, dim light extending to 20ft, but it could be at any dimness below that, and in some circumstances it can be much brighter. Mostly it depends on how fresh and fast the source is; the slower the flow, the more encrusted and darker it will be. I highly recommend doing an image search in your web browser.