Typically Botox can take up to 2 weeks for full effect. I would follow up with your doctor in a week to see if you need more units to the forehead. I usually have my new patients follow up with me after 2 weeks.
Neuromodulators, such as Botox and Xeomin, may take anywhere from 1 to 14 days to produce a visible effect. Do not panic if you have not yet seen a change at 6 days; it may still happen. I have seen patients at 10 days who had not yet seen a change and then returned at 14 days happy with their result. Sometimes when long standing wrinkles may have "etched" into the skin; that is the wrinkle producing muscles may be relaxed, but there is still a superficial line remaining. If that remains bothersome, one can be treated with a hyaluronic gel filler, such as Belotero or Juvederm to fill the line.