Without seeing a pic of it, it's hard to say what the cost to repair would be but in that area, I wouldn't wait too long. I'd get it to a luthier and get it stopped and fixed right while it's around a $100-150. since you say, it might go into the soundpost area. I'm thinking it has started at the edge down by the chinrest clamps.

He will no doubt have to split the top and bottom apart to properly clamp and glue it but maybe you can get lucky and it can be clamped without splitting the case.

The cost to split is usual in the $100 range for most home grown luthiers. Some of the high end places will charge twice or triple that.

Plan on it being non-playable for a week or two depending on their schedule of work.

Please don't think for a moment you can fix it with superglue... It won't work and is certainly not proper. If it's truely a 1890 violin, give it the care it deserves...