Yes — in Manual exposure mode, you can still adjust flash output. On the D7000, use flash exposure compensation to reduce the built-in flash power; this works in P/A/S/M modes and can be lowered by up to about 3 stops.

A key point: your camera’s exposure meter reflects the ambient light exposure, not the flash contribution. So if your manual settings already expose the scene correctly, the flash adds extra light and can overexpose the photo. In low light, a better approach is usually to set your manual exposure a bit darker for the ambient light, then let the flash fill in the subject.

If it still blows out highlights, the built-in flash may simply be too strong at close range, even at low power. Metering can also be fooled by very dark scenes and cause too much flash.

Practical tips:

• Reduce flash output with flash exposure compensation.
• Don’t rely only on the meter for flash shots.
• Try exposing the background slightly under, then add flash.
• For portraits in dark settings, shutter speeds around flash sync speed are commonly used.

Also, the pop-up flash is limited; an external flash gives much better control for low-light portraits.