A lifetime ago when I was in school, i was employed at a company that built circuit boards for their own equipment. Most that I worked on were through hole soldering of wires, but we did wave a wave solder and surface mount (smd) soldering lines. A common thing with all of these was flux. Flux is used to clean and aid in the purity of the soldered joint. Our wave solder and SMD boards all went through a washing cycle that removed the flux. The hand built portion of the boards, were cleaned with an acid brush and Isopropyl Alcohol. Dried flux can be a mix of tacky glue like substance and dry flaky stuff, is not conductive but it is ugly. Looking around the main blob, there appears to be some of this in the ICs and capacitors.
It looks like a spot of some fluid (oil, grease, something like that) rather than a damaged component. The resistors, capacitors and IC's all look fine. It also isn't likely to be very conductive in it's dried form. If you wanted you could probably clean it off with some Isopropyl alcohol on a cotton bud, but it's not something to worry about most likely.
