You have to check if your nvidia-driver and cuda versions are compatible with the pytorch version you want to install. I have pytorch=1.2 with cuda 10 and nvidia-driver 410 on my system. I think you can use this command if your nvidia driver and cuda versions are as I mentioned:
conda install pytorch==1.2.0 torchvision==0.4.0 cudatoolkit=10.0 -c pytorch