What would cause numbness in the tip of the toes?

Many possibilities. Numbness can occur from various reasons. Some potential causes include vitamin deficiency, nerve damage, nerve compression, and alcohol over consumption, side effects of different medications, or as a result of different systemic medical conditions such as diabetes. Get evaluated by a professional to determine the diagnosis. Treatment is based on the diagnosis.
A number of things. They can include tight fitting stockings and/or shoes, overuse, neuropathy from diabetes or other medical reasons, a local nerve issue such as a neuroma or tarsal tunnel syndrome, radiculopathy- nerve issues in the low back or leg (such as sciatica) that refer pain down. I would suggest that if it persists more than a couple of days and/or gets worse, to seek a podiatrist.