How can I kill these bugs?

I found these bugs on my flowering plant last week, I removed some of them, do i have to spray it with something? and do I need to flush it or do something before Harvesting?

That looks like scale. I've never dealt with it on MJ. Search "scale" and I'm sure you'll find some suggestions.

Several well-known remedies can be used to eliminate scales from a houseplant. However, there is no easy cure for a scale bug infestation. One possibility is to pick off or gently scrub them loose from the leaves and stems. Dabbing each scale with an alcohol-soaked cotton swab is another possibility for lightly infested plants. There are also numerous chemical products available for the control of scale bugs. Insecticide sprays for houseplants are available at garden centers. Spray applications should be timed to coincide with the crawler stage, which is most susceptible to insecticides. Insecticides must be applied thoroughly each week for a month or more for the greatest results.

Hopefully you'll annihilate the mofo's before they do too much to your girl. Kill the bastards and keep your plants healthy

look like mealy bugs, which are a scale, as scrog said. if you have the time and patience then do as he said with the cotton swab and alcohol.
spraying with neem oil weekly will help with control, also.
if the infestation gets serious, try "target" spraying with liquid seven. it works great but remember it is a pesticide. iGL