There are some ways to mitigate an excessive contrast. When the contrast is really heavy, the best is to combine some of them: if you use too heavily a single setting, the brightest parts of your picture may grayed.
- By the Curves and/or Levels adjustment layer, with a selection of the darkest or brightest parts of your picture (Image > Apply Image - check "Invert" to select the bright parts of your picture, don't check it to select the dark parts).
- By the modes: copy/paste your layers (Shift/Ctrl/Alt/E), use a Multiply mode to darken the brightest parts of your picture (Image > Apply Image - "Invert"); and a Screen mode to lighten its darkest parts (Image > Apply Image).
- By the Shadows/Highlights setting: copy/paste your layers (Shift/Ctrl/Alt/E), Image > Adjustments > Shadows/Highlights.
- By the HDR Toning: duplicate your picture and flatten it. Then go to Image > Adjustments > HDR Toning. Low the saturation to 0 and, eventually, increase the details. Then select all the picture and copy it. Paste it over the layers of your original picture with a soft light mode and a low opacity.