If the head is physically able to reach the whole bed of 240 x 240 mm, the answer is yes, you can change the printing area. But, the downside is that you need to change your firmware for it. This generally implies that you need to configure the firmware yourself, rather than flashing a ready made solution; this is a skill you need to have or develop. It involves downloading development software (e.g. Visual Studio Code, with addons) and printer firmware source code (e.g. Marlin 2.x). It requires you to configure the settings in the Configuration.h and Conffiguration_adv.h. You can find many of these settings in preconfigured configuration files, e.g. here: config/examples/Creality/Ender-3 Pro.
You find that recent configuration files already use a bed size of 235:
// @section geometry
// The size of the printable area
#define X_BED_SIZE 235
#define Y_BED_SIZE 235
// Travel limits (linear=mm, rotational=°) after homing, corresponding to endstop positions.
#define X_MIN_POS 0
#define Y_MIN_POS 0
#define Z_MIN_POS 0
#define X_MAX_POS X_BED_SIZE + 10
#define Y_MAX_POS Y_BED_SIZE
#define Z_MAX_POS 250
From X_MIN_POS we read that there is no extra space, the endstop marks the start of the bed, so if this is exactly the position of the start of the bed area, you probably cannot center your print area, but, it is added below for application in case there is space left. If the nozzle is above the bed when hitting the X endstop (so not exactly at the start of the print area), you cannot use the full 240 as you cannot define a negative offset as this goes past the endstop.
So, for printers that have additional space on the X axis, it is very important (when you use the whole bed) to center the printable area exactly in the middle of the building plate, see How to center my prints on the build platform? (Re-calibrate homing offset). This may imply that you need to adjust the endstop offsets.
Furthermore, you need to define the correct probing area for your build plate, see How to set Z-probe boundary limits in firmware when using automatic bed leveling?. Note that it is far more easy in Marlin 2 to specify the probing area.
Once configured, you need to build the firmware, flash the controller board, load the default settings, re-calibrate your probe Z-offset and bed center and start using the whole printing area (don't forget to change the slicer bed dimensions).
