How do do a pcolorm of an array with NaNs?

I exported a mask from a coarser resolution to a finer resolution grid.

The grid with finer resolution is a lon x lat grid of size 1440x121 covering my domain.

I want to do a pcolorm(lat,lon,Z) over the region covering this given mask.

Since the mask is from a coarser resolution, the lat, lon and Z over the mask are filled with NaN and I can't get pcolorm to work properly.

I have:

-latitude (updownLat) and longitude (updownLon) coordinates for my points of interest (mask);

-the corresponding pressure values at each point of interest (mslp1Arctic);

-1440x121 matrix for the latitude at each grid cell (latMat);

-1440x121 matrix for the longitude at each grid cell (lonMat);

-1440x121 matrix with pressure values at each grid cell (mslp1);

-1440x121 matrix with the latitude values only at the coordinates of the points of interest and NaN elsewhere (latMatMask);

-1440x121 matrix with the longitude values only at the coordinates of the points of interest and NaN elsewhere (lonMatMask);

-1440x121 matrix with the pressure values only at the coordinates of the points of interest and NaN elsewhere (mslp1Mask);

I wish to plot a pcolorm(latMatMask,lonMatMask,mslp1Mask) with all the mslp1 values in the region covered by the mask.

% Figure I want to do
figure(1);
hold on;
axesm('MapProjection','eqdazim','MapLatLimit',[60 90]);
axis off;
framem on;
gridm on;
mlabel on;
plabel on;
setm(gca,'MLabelParallel',0);
%plotm(updownLat,updownLon,'.'); %Domain where I want to do the pcolorm (mask)
%pcolorm(latMatMask,lonMatMask,mslp1Mask); %NOT WORKING
%colormap(parula);
%cb = colorbar;
geoshow('landareas.shp','FaceColor',"none",'LineWidth',1);
axis off;
set(gca,'Fontsize',15);
gcf;

I have attached an image for a better visualisation of what I wish to do (matlabQuestion.png).

Thank you! :)