IMO *saw*dust and glue looks bloody awful. If you have dust from the sander,
it looks marginally better but still not remotely similar to the boards
themselves.
I would lift and re-fix wherever possible, or fill with 2mm or 3 mm strips
if you have a sawbench handy (and the gaps are reasonably uniform), or match
a proprietary filler to the finished surface (not the bare wood) as a last
resort.