Agree with above. Cucurbitae, that is squash, pumpkins, watermelons, etc, have separate male and female flowers. The pollen has to get from the first to the second, usually by bees. You can identify the female flowers, because they come with a little embryo fruit behind them.
It is not uncommon for them to produce only male flowers for the first couple weeks that they start blooming. One theory is that this helps attract the bees so that they are on the job and ready when the females appear. If you have male and female flowers and bees or other pollinators around, you won't need to worry about hand pollinating... nature will do the job.
One meter is still a very small young watermelon plant, unless you are growing some dwarf variety. Remember this thing is going to get huge!