This does look like some kind of flare, I can't tell if this is caused by the lens or the UV filter but filters (especially "not so expensive" ones) are know to cause flare.
To avoid flare you just have to prevent the light coming directly from the sun from hitting the front of your lens, this is what the lens hood does when the sun is outside the frame.
When the sun (or any light source) is in the frame remove your UV filter and try different angles, changing the lightsource-lens angle will move the flare in the image, you can either try to minimize it or to use it for artistic purposes.
And always remember - never look at the sun trough the camera's viewfinder, use live view (and preferably sunglasses too)