I do not think you can tell if an inclusion is toxic by looking at it. I have stones with similar looking wires that are not toxic, one that is. Many such wires will "shine" after use because they get polished and they are basically glass - by definition toxic. But many are thin/small/friable enough that they can't support themselves and wear with the rest of the stone and may pose no issue. Some lines could also have rougher grit in them.
But if you can feel it, that's not a good sign unless it is lower than the hone surface. Take a razor and do circles and ellipses on slurry away from the line and then inspect the bevel under magnification. Then do some on the line and inspect the bevel under magnification. If the line is toxic, you'll see scratches etc on the bevel.
If you do see scratches on the bevel, you have some choices. 1) return the stone, 2) lap and use the back if it is flat enough and free of inclusions, 3) lap past it, or 4) pick the line. I can't tell in your image, but it looks like the line is possibly shallow.
To pick a line, take a carbide scribe and push the point straight down on the offending inclusion until it fractures. You'll have a tiny "dot" where you did this. Do this along the entire line until you have a series of connected dots that are now lower than the stone. Then take the scribe at 45 degrees and LIGHTLY trace along the line, using the scribe to "knock" the sharp corners off the line and dislodge any remaining funky particles. DO NOT try to go along the line first, it just seems to make a mess of things. Finally, take a nagura and with slurry rub the area of the line, the slurry will help smooth things off.
Then test again. If you want me to take a look at the stone and give you an opinion, I'd be glad to do that, just cover the shipping.
Cheers, Steve