Two herbs that are very common here-about are comfrey and sassafras. Both are held in high esteem by the traditional herbalist for a number of reasons. I'm writing about them together for a single reason. Both are considered dangerous if ingested, that is taken as a tea or in a capsule. However, this isn't the whole story.
The old ones thought comfrey (Symphytum officinale) when used internally was good as a blood purifier. As far as we can tell in this day, a blood purifier wasn't a cleanse, but an herb that would kill syphilis. Some believed it was good for respiratory ailments, but this was a minority. Most all used it externally for mending cuts, bruises and for "mending bones." The old names for comfrey reflect this, for instance: boneset, bruisewort, knitbone and ass ear. OK, I threw that one in just to keep your attention, though that it has been called.
Comfrey won't help heal the bone, just the bruising and trauma around it. In fact the external use has been approved by the German Commission E for bruises, strains and blunt trauma. It is usually in a cream or ointment form nowadays. Please do not take this herb internally if you value your liver, white blood cells, kidneys, lungs and GI tract.
Sassafras (Sassafras albidum) is a delicious tea slightly astringent and remarkably like root beer. In the old days, sassafras is what root beer was made from. It was used as a spring tonic and a "blood purifier" (see above). Our government took this herb off the Generally Recognized as Safe list (GRAS) a while back. It seems it contains compounds known to be carcinogenic. But then so do bacon and bologna. In balance, our government did take cyclamates off the market for the same reason. How much will hurt? we don't know for sure. Caution and discretion are in order.