Since 2 days, i see blood (black/red) in my phlegm when i clear my throat. also some traces in my snot. chest x-rays came back normal, no sign of infection. what can it be? only thing was day before, i was cutting wood w/o mask for a few seconds?

Bronchitis that is inflammation of the airways could cause bloody sputum. However CXR is not a good way of evaluating because it is not sensitive in finding pathology. If you do not smoke, exposed to dust associated with cancer like asbestos, nor have family history of cancer you probably do not need to be stressed because it may just have been dust related inflammation that is likely to resolve.