Touch and go about this one
As a Dash-8 pilot by profession, and I've heard of this happening on a few occasions. It is common for this to happen, but nothing to worry about, because the aircraft travels too slowly, and the landing is far too bumpy for it to effect the aircraft.
It's probably been caused by wear-and-tear. The worst damage sparks could do to the D8 from the N-Gear would probably be wearing the tyres, and making them a bit on the hot side. It isn't anything to worry about unless somebody has left a lot of fuel on the runway, causing an explosion...which is very unlikely, unless Jeremy Clarkson Drives that Porsche he got for £1500, on the runway, more often than constantly.
Only report this incident if there was more than one spark
Hope this puts your mind to rest...